Forces
50 exam-style questions with answers for 4.5 Forces in AQA GCSE Physics (spec 8463). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.
All 50 questions and answers
Question 1 · Spec 4.5.1.1 · Scalars and vectors
What is the difference between a scalar and a vector? [2 marks]
Answer:A scalar has magnitude only (1); a vector has magnitude and direction (1).Question 2 · Spec 4.5.1.1 · Scalars and vectors
Classify speed, velocity, mass and force as scalar or vector. [2 marks]
Answer:Scalar: speed and mass (1); vector: velocity and force (1).Question 3 · Spec 4.5.1.2 · Contact forces
Give two examples of contact forces and two of non-contact forces. [2 marks]
Answer:Contact: friction, air resistance, tension, normal contact force (1); non-contact: gravitational, electrostatic, magnetic (1).Question 4 · Spec 4.5.1.3 · Weight
State the equation for weight. [1 mark]
Answer:Weight = mass × gravitational field strength (W = mg).Question 5 · Spec 4.5.1.3 · Weight
Calculate the weight of a 70 kg person on Earth. g = 9.8 N/kg. [2 marks]
Answer:W = 70 × 9.8 (1); = 686 N (1).Question 6 · Spec 4.5.1.3 · Weight
What is the difference between mass and weight? [2 marks]
Answer:Mass is the amount of matter in an object, measured in kg, and does not change (1); weight is the force acting on it due to gravity, measured in N, and depends on g (1).Question 7 · Spec 4.5.1.4 · Resultant force
A 20 N force acts to the right and an 8 N force to the left. Calculate the resultant force. [1 mark]
Answer:12 N to the right.Question 8 · Spec 4.5.1.4 · Resolving forces · Higher only
How can a single force be resolved into two components? [1 mark]
Answer:Into two forces at right angles to each other, which together have the same effect.Question 9 · Spec 4.5.2 · Work done
State the equation for work done. [1 mark]
Answer:Work done = force × distance moved along the line of action of the force (W = Fs).Question 10 · Spec 4.5.2 · Work done
Calculate the work done to push a box 6 m with a force of 25 N. [2 marks]
Answer:W = Fs = 25 × 6 (1); = 150 J (1).Question 11 · Spec 4.5.3 · Elasticity
What is the difference between elastic and inelastic deformation? [2 marks]
Answer:Elastic deformation: the object returns to its original shape when the force is removed (1); inelastic: it does not (1).Question 12 · Spec 4.5.3 · Hooke's law
State the equation for Hooke's law. [1 mark]
Answer:Force = spring constant × extension (F = ke).Question 13 · Spec 4.5.3 · Hooke's law
A spring with k = 40 N/m is stretched by 0.15 m. Calculate the force. [2 marks]
Answer:F = ke = 40 × 0.15 (1); = 6 N (1).Question 14 · Spec 4.5.3 · Limit of proportionality
What happens beyond the limit of proportionality? [1 mark]
Answer:Extension is no longer directly proportional to force; the graph curves.Question 15 · Spec 4.5.3 · Required practical 6
Describe how to investigate the extension of a spring. [3 marks]
Answer:Hang the spring from a clamp next to a vertical ruler and record its original length (1); add masses one at a time and record the new length each time (1); calculate extension = new length − original length (1).Question 16 · Spec 4.5.3 · Required practical 6
Why should you look at the ruler at eye level? [1 mark]
Answer:To avoid parallax error.Question 17 · Spec 4.5.4 · Moments
State the equation for a moment. [1 mark]
Answer:Moment = force × perpendicular distance from the pivot (M = Fd).Question 18 · Spec 4.5.4 · Moments
A 30 N force acts 0.4 m from a pivot. Calculate the moment. [2 marks]
Answer:M = Fd = 30 × 0.4 (1); = 12 N m (1).Question 19 · Spec 4.5.4 · Moments
State the principle of moments. [1 mark]
Answer:For a balanced object, the total clockwise moment equals the total anticlockwise moment about a pivot.Question 20 · Spec 4.5.4 · Gears
How do gears transmit rotational effects? [1 mark]
Answer:A small gear driving a larger gear increases the moment (turning effect), but the larger gear turns more slowly.Question 21 · Spec 4.5.5.1.1 · Fluid pressure
State the equation for pressure. [1 mark]
Answer:Pressure = force normal to a surface ÷ area of that surface (p = F ÷ A).Question 22 · Spec 4.5.5.1.2 · Fluid pressure · Higher only
Calculate the pressure 5 m below the surface of water. Density = 1000 kg/m³, g = 9.8 N/kg. [2 marks]
Answer:p = hρg = 5 × 1000 × 9.8 (1); = 49 000 Pa (1).Question 23 · Spec 4.5.5.1.2 · Upthrust · Higher only
Explain why an object submerged in a liquid experiences upthrust. [2 marks]
Answer:Pressure increases with depth, so the pressure on the bottom surface is greater than on the top (1); this gives a resultant upward force (1).Question 24 · Spec 4.5.5.2 · Atmospheric pressure
Why does atmospheric pressure decrease with height? [2 marks]
Answer:The atmosphere gets less dense with height (1); and there is less air above, so its weight is smaller (1).Question 25 · Spec 4.5.6.1.1 · Displacement
What is the difference between distance and displacement? [1 mark]
Answer:Distance is how far an object moves (scalar); displacement is the distance in a straight line from start to finish with a direction (vector).Question 26 · Spec 4.5.6.1.2 · Speed
State typical speeds for walking, cycling and a car in town. [3 marks]
Answer:Walking about 1.5 m/s (1); cycling about 6 m/s (1); car in town about 13 m/s (1).Question 27 · Spec 4.5.6.1.2 · Speed
A cyclist travels 3 km in 10 minutes. Calculate the average speed in m/s. [2 marks]
Answer:3000 m ÷ 600 s (1); = 5 m/s (1).Question 28 · Spec 4.5.6.1.3 · Velocity
Why does an object moving in a circle at constant speed have a changing velocity? [1 mark]
Answer:Its direction is constantly changing, and velocity includes direction.Question 29 · Spec 4.5.6.1.4 · Distance-time graphs
What does the gradient of a distance–time graph show? [1 mark]
Answer:The speed.Question 30 · Spec 4.5.6.1.4 · Distance-time graphs · Higher only
How do you find the speed of an accelerating object from a distance–time graph? [1 mark]
Answer:Draw a tangent to the curve at that time and find its gradient.Question 31 · Spec 4.5.6.1.5 · Acceleration
A car goes from 0 to 24 m/s in 8 s. Calculate its acceleration. [2 marks]
Answer:a = Δv ÷ t = 24 ÷ 8 (1); = 3 m/s² (1).Question 32 · Spec 4.5.6.1.5 · Velocity-time graphs
What does the gradient of a velocity–time graph show? [1 mark]
Answer:The acceleration.Question 33 · Spec 4.5.6.1.5 · Velocity-time graphs · Higher only
What does the area under a velocity–time graph show? [1 mark]
Answer:The distance travelled (displacement).Question 34 · Spec 4.5.6.1.5 · Acceleration
A car accelerates from 10 m/s to 30 m/s over 100 m. Calculate its acceleration using v² − u² = 2as. [2 marks]
Answer:30² − 10² = 2 × a × 100, so 800 = 200a (1); a = 4 m/s² (1).Question 35 · Spec 4.5.6.1.5 · Terminal velocity
Explain why a skydiver reaches terminal velocity. [3 marks]
Answer:At first, weight is greater than air resistance, so the skydiver accelerates (1); as speed increases, air resistance increases (1); when air resistance equals weight, the resultant force is zero and speed is constant (1).Question 36 · Spec 4.5.6.2.1 · Newton's first law
State Newton's first law. [2 marks]
Answer:If the resultant force on a stationary object is zero, it stays stationary (1); if it is moving, it continues at the same speed in the same direction (1).Question 37 · Spec 4.5.6.2.1 · Inertia · Higher only
What is inertia? [1 mark]
Answer:The tendency of objects to continue in their state of rest or uniform motion.Question 38 · Spec 4.5.6.2.2 · Newton's second law
Calculate the force needed to accelerate a 1200 kg car at 2.5 m/s². [2 marks]
Answer:F = ma = 1200 × 2.5 (1); = 3000 N (1).Question 39 · Spec 4.5.6.2.2 · Inertial mass · Higher only
Define inertial mass. [1 mark]
Answer:A measure of how difficult it is to change the velocity of an object (mass = force ÷ acceleration).Question 40 · Spec 4.5.6.2.2 · Required practical 7
Describe how to investigate the effect of force on acceleration. [3 marks]
Answer:Attach a trolley to a hanging mass over a pulley and use light gates to measure its acceleration (1); move masses from the trolley to the hanger to change the force while keeping total mass constant (1); plot a graph of acceleration against force (1).Question 41 · Spec 4.5.6.2.3 · Newton's third law
State Newton's third law. [1 mark]
Answer:When two objects interact, they exert equal and opposite forces on each other.Question 42 · Spec 4.5.6.3.1 · Stopping distance
What is stopping distance? [1 mark]
Answer:Thinking distance + braking distance.Question 43 · Spec 4.5.6.3.2 · Reaction time
State two factors that increase reaction time. [2 marks]
Answer:Any two from: tiredness (1); drugs (1); alcohol (1); distractions (1).Question 44 · Spec 4.5.6.3.3 · Braking distance
State two factors that increase braking distance. [2 marks]
Answer:Any two from: wet or icy roads (1); worn brakes or tyres (1); higher speed (1).Question 45 · Spec 4.5.6.3.4 · Braking
Explain why braking at high speed can be dangerous. [2 marks]
Answer:Large decelerations need large braking forces (1); which may cause the brakes to overheat or the vehicle to skid (1).Question 46 · Spec 4.5.7.1 · Momentum · Higher only
Calculate the momentum of a 60 kg runner moving at 8 m/s. [2 marks]
Answer:p = mv = 60 × 8 (1); = 480 kg m/s (1).Question 47 · Spec 4.5.7.2 · Conservation of momentum · Higher only
State the principle of conservation of momentum. [1 mark]
Answer:In a closed system, the total momentum before an event equals the total momentum after.Question 48 · Spec 4.5.7.2 · Conservation of momentum · Higher only
A 2 kg trolley at 3 m/s hits and sticks to a stationary 1 kg trolley. Calculate their speed. [2 marks]
Answer:Momentum before = 2 × 3 = 6 kg m/s (1); 6 = 3 × v, so v = 2 m/s (1).Question 49 · Spec 4.5.7.3 · Changes in momentum · Higher only
Explain how a car airbag reduces injury. [2 marks]
Answer:It increases the time taken for the change in momentum (1); so the force on the passenger is smaller (F = Δp ÷ t) (1).Question 50 · Spec 4.5.7.3 · Changes in momentum · Higher only
Name two safety features that work by increasing the time of a collision. [2 marks]
Answer:Any two from: seat belts (1); air bags (1); crumple zones (1); cushioned gym mats (1); cycle helmets (1).